Free-radical polymerization process with bis(2-benzthiazole) accelerators



United States Patent 3,207,815 FREE-RADICAL POLYMERIZATION PROCESS WITH BIS(2-BENZTHIAZOLE) ACCELERATORS Louis A. J00, John B. Braunwarth, and Charanjit Rai, Crystal Lake, Ill., assignors to The Pure Oil Company, Chicago, 111., a corporation of Ohio No Drawing. Filed July 13, 1962, Ser. No. 209,792 Claims. (Cl. 260-862) This invention relates to new polymerization accelerators comprising bis(2-benzothiazole), oc,w-biS(Z-b6nZO- thiazolyl)alkanes, and derivatives thereof. More particularly, this invention relates to the discovery that bis(2- benzothiazole), a,w-bis(2-benzothiazolyl)alkanes, and derivatives thereof are effective polymerization accelerators for peroxide-initiated polymerizable systems.

The polymerization of certain polymerizable systems, such as resin systems containing unsaturated polyesters and cross-linking monomers, proceed by a free-radical mechanism which involves opening of the double bonds in the polyester chains or monomer. These activated radicals open other double bonds, adding to one of the electrons in the double linkage and freeing the other electron to form a new free radical. The co-polymerization reaction is commonly initiated by the addition of socalled catalysts, such as organic peroxides and hydroperoxides, which decompose to very active free radicals that become the centers for polymer growth. Although these substances are commonly known in the art as catalysts, they would better be called initiators, as proposed by the International Union of Pure and Applied Chemistry, since they take part in the reaction. Accelerators or promoters are added to such resin systems to speed the decomposition of the catalyst or initiator into free radicals at room temperature, or at temperatures considerably below those required to release free radicals when catalyst alone is used. While some of the accelerators which have been heretofore proposed or used are effective with peroxide and hydroperoxide catalysts, many are most effective with only either peroxide or hydroperoxide catalysts. For example, cobalt naphthenate is most effective with methyl ethyl ketone peroxide while dimethyl aniline is most elfective with benzoyl peroxide. A more detailed discussion of polyester catalysis can be found in Chapter 6 of Polyester Resins by John R. Lawrence, published by Reinhold Publishing Corporation, 1960, and Chapter 3 of Polyesters and Their Applications by Bjorksten, published by Reinhold Publishing Corporation, 1956.

In accordance with this invention, we have discovered that bis(2-bcnzothiazole), substituted bis(2-benzothia- .zoles), ago-bis(2-benzothiazolyl)alkanes, and substituted .a,w-bis(Z-benzothiazolyl)alkanes are effective polymerizattion accelerators for peroxide-initiated polymerizations.

It is a primary object of this invention to provide new polymerization accelerators comprising bis(2-benzothiazole), a,wbis(2-benzothiazolylalkanes, and derivatives thereof.

Another object of this invention is to provide a polymerizable system containing sufiicient amount of bis(2- benzothiazole), e o-bis(2-benzothiazolyl)alkanes, or de rivatives thereof, to accelerate the polymerization of such systems.

Still another object of this invention is to provide a free-radical-initiated polymerizable system containing a sufiicient amount of bis(2-benzothiazole), oc,wbiS(2 benzothiazolyl)alkanes, or derivatives thereof, to accelerate the polymerization of such systems.

'and cycloalkyl radicals.

Still another object of this invention is to provide a peroxide-initiated, polymerizable system containing a suificient amount of bis(2-benzothiazole), ot,w-biS(2-b6[l- 'zothiazolyUalkanes, or derivatives thereof, to accelerate the polymerization of such systems.

A still further object of this invention is to provide a method of accelerating the polymerization of peroxide- -initiated vinyl and polyester polymerizable systems by adding to the systems small amounts of bis(2-benzothiazole), a,w-bis(2-benzothiazolyl)alkanes, or derivatives thereof.

A further object of this invention is to provide a methodof accelerating the polymerization of a polymerizable system containing a peroxide initiator by adding to the system a small amount of bis(2-benzothiazole), a,w-bi$(2 benzothiazolyl)alkanes, and derivatives thereof.

These and further objects of this invention will be described or become apparent as the description herein proceeds.

The new polymerization accelerators of this invention are represented by the formula,

wherein n has a value of 0 to 12 and R and R are hydrogen, or the same or different hydrocarbon radicals containing from 1 to 20 carbon atoms. These compounds are prepared by various known methods, such as described in J. Chem. Soc., 2393 (1928) by M. A. Phillips; Ber., 13, 1231 (1880) and Ber., 20, 2251 (1887) by A. W. Hofman; J. Chem. Soc., 121,. 464 (1922) by W. A. Mills; Rai and Braunwarth, J. Org. Chem, 26, 3434 (1961); and in US. patent application 151,190, filed November 9, 1961, now abandoned. The method of preparing the instant compounds as described in said application consists of reacting an o-aminothiophenol (or polycyclic aromatic analogs thereof) with a dibasic acid in the presence of polyphosphorie acid as a catalyts. The polyphosphoric acid which is used as a catalyst in the preparation of the compounds is a commercial product consisting of a liquid mixture of polymeric phosphoric acids having a P 0 content in the range of about 72-90%, preferably about 82-84%. In general, reaction periods ranging from less than one-half hour to about two hours are adequate for the reaction to go substantially to com- 'pletion at temperatures ranging from about -200 C. The severity of conditions required to cause the desired reaction to occur depend on the specific reactant being condensed with the o-aminothiophenol, and must be selected with care to avoid undesirable side reactions.

R and R can be hydrogen or hydrocarbon radicals, such as alkyl, alkylene, aryl, aralkyl, aralkylene, alkaryl, Radicals in the aliphatic series include methyl, ethyl, propyl, isopropyl, butyl, isobntyl, t-butyl, amyl, isoamyl, t-amyl, hexyl, isohexyl, heptyl, isoheptyl, octyl, isooctyl, nonyl, isononyl, decyl, ethenyl, butenyl, butadienyl, isoheptenyl, etc. The aryl groups includes phenyl, biphenyl, napthyl, anthryl, etc.; the a-rylsubstituted aliphatic radicals include benzyl, phenylethyl, phenylethenyl, phenylbutadienyl, etc.; the aliphatic-substituted aryl radicals include tolyl, xylyl, butenylnaphthyl, butadienylnaphthyl, etc.; and the cycloalkyl radicals include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl radicals. Radicals in the aliphatic series are preferably limited to those containing up to carbon atoms. From the above definition, it will be apparent that polycyclic aryl radicals and aliphatic-substituted derivatives thereof can be attached to the thiazole groups.

Species of compounds that come within the foregoing definition when R and R are hydrogen are:

Bis 2-benzothiazole) Bis (Z-benzotbiazolyl methane 1,2-bis Z-benzothiazolyl ethane 1,3-bis (2-benzothiazolyl propane '1,4-bis Z-benzothiazolyl) butane 1,5 -bis (Z-benzothiazolyl pentane 1,10-bis (2-benzothiazolyl) decane 1,12-bis(2-benzothiazolyl)dodecane Examples when R and/ or R are aliphatic radicals are:

Bis- 2- 4-methyl benzothiazole] Bis- [2- 6-ethenyl benzothiazole] Bis-[2-(7,7-dirnethyl)benzothiazole] Bis- [2- 5 ,7 -diethyl benzothiazole] Bis- [2- S-butadienyl benzothiazole] Bis- [2-(4-methyl,6-nonyl,5-ethyl,7-decyl)benzothiazole] Bis- [2-( 5-ethyl)benzothiazolyl]methane -Bis- [2- 6,6'-dimethyl benzothiazolyl] methane 1,2-bis- [2- (4,5-dioctyl benzothiazolyl ethane 1,2-bis- [2- 4,4',6,6'-tetraisopropyl benzothiazolyl] ethane 1,3-bis- [2- 6,6'-dihexyl benzothiazolyl] propane 1,3-bis- [2- 5 ,6-di-t-butyl) benzothiazolyl] propane 1,4-bis- [2- (4-methyl,5-butyl,6'-propyl) benzothiazolyl] butane 1,5-bis- [2- 5- 1,3 -butadienyl) ,7'-heptyl benzothiazolyl] pentane 1,10-bis- [2- (4,4-dioctyl)benzothiazolyl] decane 1,9-bis- [2- 4,5 ,6',7'-tetramethyl benzothiazolyl] nonane .1,2-bis-[2-( 5 -methyl)naphthothiazolyl]ethane 1,5-bis- [2-(4-ethyl-8'-methyl)naphthothiazolyl1pentane 1,3 -bis- 2- (4-pheny1ethenyl naphthothiazolyl] propane 1,4-bis-[2-(6,9'-dipropyl)naphthothiazolyHbutane .1,5-bis- [2-(4,8-dirnethyl,5-ethyl)naphthothiazolyl] pentane Bis- [2-(6,8-diethyl-4',9-dimethyl)naphthothiazolyl] methane Examples when R and/ or R are aryl radicals are:

Bis- [2- (4-phenyl benzothiazolyl] methane 1,7-bis- [2- 5,7'-diphenyl benzothiazolyl] heptane 1,8-bis- [2- 4-phenyl,5 -biphenyl benzothiazolyl] octane 1,7-bis-[2-(6-naphthyl)benzothiazolyl1heptane Bis 2-naphthothiazolyl methane 1,2-bis-(Z-naphthothiazolyl)ethane 1,3-bis(2-naphthothiazolyl) propane 1,5-bis 2-naphthothiazolyl pentane 1,10-bis(Z-naphthothiazolyl)decane v 1,3-bis- [2-( S-phenyl)naphthothiazolyl] propane 1,6-bis- [2- (4,7'-diphenyl )rnaphthothiazolyl] hexane 1,4-bis- 2- 6-phenyl,5'-biphenyl naphthothiazolyl] butane 1,3-bis- [2-( S-naphthyl)naphthothiazolyl] propane Bis- [2- S-phenyl benzothiazole] Bis- [2-(4,7-diphenyl) benzothiazole] 1,2-bis(2-anthrothiazolyl)ethane phatic radicals are:

Bis- [2- 6-benzyl) benzothiazole] Bis- [2- 5-phenylethyl,6'-benzyl benzothiazole] 1,4-bis- [2- S-benzyl benzothiazolyl] butane I 1,6-bis- [2- 6-benZyl-7'-benzyl) benzothiazolyl] hexane 1,8-bis- [2- (7-pl1enylethyl benzothiazolyl] octane 1,5-bis- [2-(5-styryl)benzothiazolyl] pentane Bis-[2-(6-phenylethyl-4-benzyl)benzothiazolyl) methane Examples when R and/ or R are aliphatic-substituted aryl radicals are:

Bis-l 2- [4-(m-ethylphenyl) ]benzothiazole] 1,4-bis-I2- [5- p-vinylphenyl) ]benzothiazolyl|butane 1,5 -bis-[2- [6,6'-di (m-propylphenyl) Jbenzothiazolyl] pentane 1,7-bis-[2- [7-(p-ethyphenyl) ]naphthothiazolyllheptane 1,3 -bis-[2- 5,8'-di (m-ethylphenyl) [naphthothiazolyl] propane 1,8-bis-| 2- 6- (p-tolyl] naphthothiazolylloctane 1,10-bis-[2-17-(m-cumyl) lnaphthothiazoylldecane Example when R and R are mixed aliphatic cycloalkyl, or aryl radicals are:

Bis- [2- 5-ethyl-6"-phenyl benzothiazole] Bis- 2-( 4,5 -dimethy1,6-cyclopentyl benzothiazole] Bis- [2- 4-methyl-4'-phenyl benzothiazoyl] methane 1,3-bis- 2- 5-t-butyl-6naphthyl) benezothiaz-olyl] propane 1,4-bis- 2- 6,7-diethyl, 4'-phenyl benzothiazolyl] butane 1,5 -bis- [2-(4-cyclohexyl,5 '-lphenyl )benzothiazolyl] pentane 1,6-bis- 2- 5-me.thyl,6-phenyl,4'-ethyl,7'naphthyl) benzothiazolyl] hexane 1,7-bis- 2- (4,5 ,6,7-tetraethyl,4'-cyclohexyl) benzothiazolyl1heptane 1,2-bis- [2- 5-methyl,8-phenyl naphthothiazolyl] ethane 1,3-bis- [2- 6-ethenyl,7 '-phenyl naphthothiazolyl] propane 1,4-bis- 2- S-cyclohexyLS '-phenyl naphthothiazolyl] butane 1,5 -bis-[2-(7-ethyl, 8'-naphthy1)naphthothiazolyl] pentane 1,1-bis-[2-(6-(2,4-pentadienyl),7-phenyl) naphthothiazolyl] hexane In accordance with our invention, any one or mixtures of two or more of the foregoing compounds are added in a small amount to a polymerizable system containing a peroxide catalyst. The amount utilized will be varied depending on such factors as the polymerizable compounds used, reaction products desired, catalyst used, reaction temperature, etc. The accelerators are preferably added in an amount of about 0.001% to 5.0% by weight of the polymerizable materials since no particular advantage is gained by using greater amounts. The novel polymerization accelerators serve to speed the decomposition of the catalyst or initiator into free radicals, which become centers for polymer growth, at room temperature or at temperatures considerably below those required to release free radicals when the catalyst alone is used.

In some instances, the solubility of the specific polymerization accelerator utilized in a particular polymerizable system will limit the range of concentrations practicable. As shown in Table I, bis (2-benzothiazole) is characterized by low solubility in styrene at low temperatures. Higher temperatures, hydrocarbon substituents on the benzene ring of the benzoth-iazole, or a methylene chain between the benzothiazolyl groups will permit a wider range of concentrations of the polymerization accelerator to be used.

Table l Gm. bis(2-benzothiazole) Temperature, C.: g. styrene Care should be taken in the addition of the catalyst and accelerator to the resin system. For example, adding a peroxide catalyst with an accelerator to a polymerizable system might result in an explosion. One acceptable method of adding the catalytic substances is to add the catalyst first, mix it in well, and then add the accelerator. Another method is to divide the resin system into two parts, one of which is usually larger than the other, mix

2,5-diol, 2-butene-1,4-diol, etc.; saturated dihydroxy compounds such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, etc.; and monohydric alcohols which are used as modifiers, such as n-butanol,

5 propanol, isopropanol, 2-ethyl hexanol, etc.

the catalyst into the larger part and the accelerator into The term acid as used herein is intended to cover the the smaller part, and combine the two parts. The cataanhydride as well as the acid since the anhydride may be lytic substances must be evenly and thoroughly distribused whenever available and desirable. uted throughout the resin to avoid local saturation and Illustrative of unsaturated polyester resins are propylresulting hard spots. At the same time, the agitation 10 ene glycol maleate, diethyl fumarate, diethyl maleate, dimust not be so violent as to introduce air into the resin butyl fumarate, ethylene glycol fumarate, diallyl maleate, since the trapped air will result in voids in the product. diallyl fumarate, dimethallyl maleate, etc.

Peroxide-initiated polymerizable compounds with which Some of the peroxides which may be utilized as catalysts the novel polymerization accelerators of this invention are or initiators in accordance with this invention in conjuncuseful include the various polymerizable monomers and tion with the polymerization accelerators are: cumene mixtures of monomer-s. These include the various hydroperoxide, dichloro-benzoyl peroxide, tertiary butyl polymerizable monomers having a terminal ethylenic hydroperoxide, benzoyl peroxide, tertiary butyl perbengroup i.e., CI-I =C such as styrene; substituted styzoate, acetyl benzoyl peroxide, caprylyl peroxide, lauryl renes, e.g., divinyl benzene, alpha-methyl styrene, vinyl peroxide, hydroxyheptyl peroxide, methyl ethyl ketone toluene, dichlorostyrene, vinyl ethylbenzene, etc.; vinyl peroxide, l-hydroxycyclohexylhydroperoxide-l, ditertiary halide compounds, e.g., vinyl chloride, vinylidene chlobutyl perphthalate, dibenzaldiperoxide, tertiary butyl ride, vinyl bromide, etc.; diolefin compounds, e.g., butaperoxide, 2,2-(tertiary -butylperoxy)butane, bis(para dime-1,3, Z-methyl butadiene-1,3 chloroprene, Z-cyanobromobenzoyl)peroxide, bis(para-chlo.robenzoyl)peroxbutadiene-l,3; vinyl ethers and esters, e.g., divinyl ether, ide, bis(succinyl) peroxide, and bis(chloroacetyl)peroxvinyl acetate, vinyl propionate, vinyl acrylate, divinyl ide, as well as said peroxide catalysts compounded with oxalate, etc.; vinyl ketones, e.g., divinyl ketone, vinyl other compounds, such as benzoyl peroxide compounded ethyl ketone, etc.; acrylic and methacrylic acids and dewith tricresyl phosphate, benzoyl peroxide compounded riv-atives thereof including the nitriles of said acids, e.g., with dibutyl phthalate, methyl ethyl ketone peroxide in acrylonitrile, the amides of said acids, e.g., acrylamide, dimethyl phthalate, and cyclohexanone peroxide comesters, of an acrylic acid, e.g., ethyl acrylate, butyl acrypounded with dibutyl phthalate. In general, the peroxide late, methyl methacrylate, propyl methacrylate, propyl initiators are added to the polymerizable system in an alpha-chloroacrylate, benzyl acrylate, chlorobenzyl acryamount from about 0.1 to 10% by weight of the polymlate, etc.; polyesters of acrylic acids, e.g., ethylene diacryerizable materials, with a range of about 0.25 to 5% belate, etc.; allyl and methallyl ethers and allyl and methaling preferred. Y esters of monocarboxylic and polycarboxylic saturated In order to demonstrate the effectiveness of the novel and unsaturated acids, -a Vinyl allyl ether, dihnyl polymerization accelerators of this invention, experiments Rhthalate, diauyl Carbonate, diauyl maleflte, and the were conducted in which .styrene was polymerized at ambient and elevated temperatures. In one series of ex- The novel holymenzatlon,aFFflQPatOTS are F useful periments, small amounts of 1,2-bis(2-benzothiazolyl)- where a peroxide is used to init ate the cross-linking of a 4-0 ethane as a typical example of the polymerization i unsaiurated polyester resm With a monomer i celerators of this invention, were added to two separate a termmgl eflllylemiz gioup to f a gi i portions of styrene, containing 0.3% by weight of methyl R ymer' T 6 p0 MHZ-anon W efatorsof t is mvim ethyl ketone peroxide, in amounts of 0.01% and 0.20% tion may also be used in combination with a peroxide b ht Th th 1 t d t t catalyst to cause a certain amount of reaction between y Welg 6 u t were, 5 ore P em double bonds in linear polyester resins resulting in the perature: h vlscosmes are n d1cahve of formation of a cross-linked structure. Polyester resins polymenzatloh, Wem checked n dlcally uslng a Gardare the polycondensation products of dicarboxylic acids Der hh Vlscometer- The Vlscoslty 0f the f q with dihydroxy ,a1coho1S These Compounds may containing styrene solutions was compared with the V15- modified by monocarboxylic acids, monohydroxy alco- 5O cosity of a third portion of styrene containing only methyl hols, and even small amounts of polycarboxylic acids or ethyl ketone peroxide. The results are given in Table II.

Table II t l t Accelerator Viscosity (stokes) after- Sample concentration, collcellitfgzlon,

Number Catalyst Accelerator I Eic ent 4 days 5 days 7 days 9 days 1 Methyl ethyl ketone 0.3 None peroxide. I 2 do 0.3 1,2-bis(2-benzo-th1a- 0.01 0.5 0.69 2. 45 8.9

zOlyDethane.

3 d0 0.3 do 0.20 0.58 1.32 6.7 36.0

polyhydroxy alcohols. The unsaturated polyester resins In order to compare the effectiveness of our accelerators are d d h any of th reactants t i with known commercial accelerators, another series of matic unsaturation. Examples of acids used in the prepexperiments was conducted in which the effectiveness of aration of polyesters are unsaturated dibasic acids, such biSQ-bBHZOthiHZOIE) and 1,2-bi$(2-benlothialolyl)ethane as maleic acid, fumaric, chloromaleic, itaconic acid, was compared with cobalt naphthenate in separate samcitraconic acid, etc.; saturated dibasic acids, such as sucples of styrene containing 1.0% by weight of methyl ethyl cinic acid, glutaric acid, adipic acid, pimelic acid, suberic ketone peroxide, and with dimethylaniline in separate acid, etc.; and monocarboxylic acids which are utilized as samples of styrene containing 1.0% by weight of benzoyl modifiers, such as acetic, caproic acid, lauric acid, myrisperoxide. The samples were maintained at 80 C., and tic acid, oleic acid, etc. Alcohols used in the preparathe viscosities were checked every two hours using a tion of polyester resins include unsaturated dihydroxy Gardner Bubble Viscometer. The results of this series compounds, such as allyl alcohol, 2,5-dimethyl 3-hexyneof experiments are given in Table III.

Table III Catalyst Accelerator Viscosity (Stokes) After Sample Catalyst COHCGIIlJTtEIOII, Accelerator concentrgttmn,

' Wei Number p ei c ent perc ent 2 hours 4 hours 6 hours 8 hours 10 hours 4 Methyl ethyl ketone 1. Cobalt naphthenate- 1. 0. 5 0.5 1. 6 5.2 17.0

peroxide.

5 dn 1. 0 Bis(2-benz0thiazole) 0. 33 0. 5 0.87 5. 0 40. O (Gelled) 6 r1n 1. 0 1,2-bis(2-benzothiazolyl)- 1. 0 0. 5 0. 5 4. 6 (Gelled) (Gelled) ethane.

"d 1.0 D" eth lanilino 1.0 0.5 0.5 0.6 1.2 2.4 5.-.": .FffiifiifffTf 1. 0 Bi; 2-be i1z0thiazole) 0.33 0. 5 3. 7 82.0 (Gelled) (Gelled) o dn 1. 0 1,Z-bisQbeuzothiazolyl) 1. 0 0. 5 0. 5 5.9 (Gelled) (Gelled) ethane.

From an inspection of Tabl 11 d 111, it will b seen 15 lymerizable system, in an amount sufiicient to accelerate that the instant compounds, as represented by bis(benzothiazole) and 1,2-bis(2-benzothiazolyl)ethane are efiective accelerators for peroxide-initiated polymerizable systems. Referring to Table II, Sample Number 1, which contained the catalyst but no accelerator, had a viscosity of 6.4 stokes after 9 days, whereas Samples 2 and 3, containing 0.01 and 0.20% by weight, respectively, of the accelerator had viscosities of 8.9 and 36.0 stokes. Referring to Table III, the addition of 1.5% by weight of cobalt naphthenate to styrene containing 1.0% by weight of methyl ethyl ketone peroxide (Sample 4) resulted in a viscosity of 17 stokes after 10 hours. On the other hand, the addition of 0.33% by weight of bis(2-benzothiazole) and 1.0% by weight of 1,2-bis(2-benzothiazolyl)ethane to styrene solutions containing 1.0% by weight of methyl ethyl ketone peroxide resulted in gellation within 10 and 8 hours, respectively. Similar results were obtained with Samples 7, 8 and 9, where the efiectiveness of bis(2-benzothiazole) and 1,2-bis(2-benzothiazolyl)ethane were compared with dimethyl-aniline in styrene solutions containing 1.0% by weight of benzoyl peroxide.

Results similar to those depicted in Tables III and IV 'are obtained substituting other polymerizable systems for the styrene, other catalysts or initiators, and other polymerization accelerators. Examples of polymerizable systems, catalysts or initiators, and polymerization accelerators are set forth in Table IV.

the polymerization thereof, a compound of the formula,

wherein n is an integer from 0 to 12, and R and R independently of each other are a member selected from the group consisting of hydrogen and hydrocarbon radicals containing from 1 to about 20 carbon atoms; and thereafter allowing said polymerizable system to pclymer-ize.

2. A method in accordance with claim 1 in which R and R are hydrogen.

3. A method in accordance with claim 2 in which said compound is his Z-benzothiazole 4. A method in accordance with claim 2 in which said compound is 1,2-bis(Z-benzothiazolyl)ethane.

5. A method in accordance with claim 1 in which R is hydrogen and R is a hydrogen radical containing from 1 to about 10 carbon atoms in any aliphatic portions thereof.

6. A method in accordance Wit-h claim 1 in which R and R are hydrocarbons containing from 1 up to about 10 carbon atoms in any aliphatic portions thereof.

'7. A method in accordance with claim 1 in which said compound is added in amount from about 0.001% to Table IV System Polymerizable system, parts by weight Number Catalyst, parts by weight Accelerator, parts by weight Propylene glycol maleate, 70 parts; styrene,

30 parts. Acrylonitrile, 65 parts; butadiene, 35 parts Methyl ethyl ketone peroxide, 1.0 parts Lauryl peroxide, 1.0 parts Cun ene hydroperoxide, 1.0 parts Tertiary butyl hydroperoxide, 1.0 parts.

Tertiary butylperbenzoate, 1.0 parts Tertiary butyl, hydroperoxide, 1.0 parts Bis(2-benzothiazole), 0.40 parts.

Bis[2-t(5-ethyl)benzothiazolyl] methane, 0.60

ar s

p 1,5-bis(Z-benzothiazolyl)pentane, 0.60 parts. Bis[2-(4methyl)beuzothiazole] 0.50 parts.

1,4-bis[2 (6-benzyl)benzothiazolyl] butane,

0.90 arts vinylalkyd, parts.

p Bis (Z-benzothiazole), 0.35 parts.

. lows -1. In the method of polymerizing a polymerizable system, containing at least one polymerizable compound having a terminal ethylenic group, which is polymerizable in the presence of a free radical-releasing peroxide catalyst, said polymerizable system containing an effective amount of said catalyst to produce polymerization, the improvement which comprises adding to said po- 5.0% by weight of the polymerizable materials contained in said polymerizable system.

8. A method in accordance with claim 7 in which said compound having a terminal ethylenic group is styrene.

9. A method in accordance with claim 7 in which said polymerizable system consists essentially of compounds having terminal ethylenic groups.

10. A method in accordance with claim 7 in which said polymerizable system consists essentially of a compound having a terminal ethylenic group and an unsaturated polyester resin.

11. A method in accordance with claim 1 in which said catalyst is an organic peroxide.

12. A method in accordance with claim 11 in which said catalyst is selected from the group consisting of methyl ethyl ketone peroxide and benzoyl peroxide.

13. In the method of polymerizing .a polymerizable system which is polymerizable in the presence of a free radical-releasing peroxide catalyst, said polymerizable system containing at least one polymerizable compound having a terminal ethylenic group and said catalyst in an amount from about 0.1% to 10% by weight of the polymerizable materials, the improvement which comprises adding to said polymerizable system, in an amount from about 0.001% to 5.0% by weight of said polymerizable materials, a compound of the formula,

wherein n is an integer from to 1 2, and R and R independently of each other are a member selected from the group consisting of hydrogen and hydrocarbon radicals containing a total of 1 to about 20 carbon atoms, with 10 carbon atoms in any aliphatic portion of said hydrocarbon radical; and thereafter allowing said polymerizable system to polymerize.

14. A method in accordance with claim 13 in which said polymerizable system consists essentially of at least one compound having a terminal ethylenic group and R and R are hydrogen.

15. A method in accordance with claim 14 in which said catalyst is selected from the group consisting of methyl ethyl ketone peroxide and benzoyl peroxide, and said polymerizable system consists essentially of styrene.

References Cited by the Examiner UNITED STATES PATENTS 2,321,305 \6/ 43 Messer 260-7 88 2,857,358 =10/58 Thomas 2 -86=2 3,066,115 11/62 Smith et al. 26093.5

OTHER REFERENCES Mills: J. Chem. Soc., 121 (1922), page 464.

JOSEPH L. SCHOFER, Primary Examiner.

DONALD E. CZAJA, Examiner. 

1. IN THE METHOD OF POLYMERIZING A POLYMERIZABLE SYSTEM, CONTAINING AT LEAST ONE POLYMERIZABLE COMPOUND HAVING A TERMINAL ETHYLENIC GROUP, WHICH IS POLYMERIZABLE IN THE PRESENCE OF A FREE RADICAL-RELEASING PEROXIDE CATALYST, SAID POLYMERIZABLE SYSTEM CONTAINING AN EFFECTIVE AMOUNT OF SAID CATALYST TO PRODUCE POLYMERIZATION, THE IMPROVEMENT WHICH COMPRISES ADDING TO SAID POLYMERIZABLE SYSTEM, IN AN AMOUNT SUFFICIENT TO ACCELERATE THE POLYMERIZATION THEREOF, A COMPOUND OF THE FORMULA, 